Trigonelline improves mitochondrial calcium homeostasis and reduces calpain activity after skeletal muscle ischemia-reperfusion injury in mice.

Skeletal muscle ischemia-reperfusion injury (IRI) causes persistent tissue damage and functional impairment, partly through mitochondrial calcium dysregulation and calpain-mediated proteolysis. This study investigated whether trigonelline (TG), a natural alkaloid, improves skeletal muscle recovery and mitochondrial homeostasis after IRI. Male C57BL/10 mice were randomly assigned to sham control, untreated IRI, or IRI plus TG groups. After 2 h of bilateral hindlimb ischemia, mice received a single intraperitoneal dose of TG (150 mg/kg) immediately before tourniquet release and were evaluated after 7 days of reperfusion. Functional performance, serum creatine kinase (CK) activity, quadriceps mass and histology, mitochondrial respiration and calcium handling, 4-hydroxynonenal (4-HNE) levels, and calpain activity were assessed. TG did not reduce CK activity, prevent quadriceps mass loss, restore grip strength, or significantly improve mitochondrial respiration. Exploratory wheel-running data suggested faster recovery of spontaneous activity. TG increased the number of regenerating fibers and shifted the fiber-diameter distribution toward larger fibers. It also reduced alamethicin-induced mitochondrial calcium release, restored calcium retention capacity to near-control levels, and decreased calpain activity. Although 4-HNE was elevated in both ischemic groups at 2 h, it remained elevated at day 7 only after TG treatment. Thus, a single post-ischemic dose of TG selectively improved mitochondrial calcium handling and reduced calpain activity and was associated with histological features consistent with muscle repair, but did not prevent muscle loss or restore strength. These preliminary findings support further investigation of TG as a potential strategy for recovery after ischemic muscle injury.